Methods for controlling at least one actuator in a mass flow duct are already known, in which the flow resistance of the mass flow duct is modified by controlling the at least one actuator. Such an actuator is a bypass valve in a bypass, for example, which is connected in parallel to a turbine of an exhaust gas turbocharger in an exhaust system branch of an internal combustion engine. A desired boost pressure in an intake pipe of the engine downstream from a compressor of the exhaust gas turbocharger may be set by suitably controlling the bypass valve.
The turbocharged engine is currently usually regulated with regard to the boost pressure. In this case, the pressure in the intake pipe downstream from the compressor is the controlled variable and the position of the bypass valve is the manipulated variable. The delay due to the controlled system and the fact that the way the control device affects the controlled variable is reversed in certain operating ranges both result in the regulation on the basis of a physical model being very complicated. While it is possible to set the steady-state operating points using setpoint values for the position of the bypass valve or to set the boost pressure using a characteristics map, difficulties arise in dynamic operation for which such a regulation structure does not provide optimum resolution.